Which macronutrient provides about 9 kcal/g when fully oxidized?

Fats are the macronutrient that provides approximately 9 kcal per gram when fully oxidized. This high energy density is due to the molecular structure of fats, which contain long chains of hydrocarbons. When these fats undergo metabolic processes, they release a significant amount of energy compared to other macronutrients.

In contrast, proteins provide about 4 kcal/g, which is a result of their unique structure and function in the body primarily related to tissue repair and enzyme production. Carbohydrates also yield around 4 kcal/g, serving as the body’s primary and preferred source of energy, particularly for high-intensity activities. Vitamins, on the other hand, are micronutrients that do not provide calories at all; instead, they support various biochemical reactions in the body without being a direct energy source.

Understanding the caloric value of these macronutrients is crucial in nutrition, especially when considering energy needs and dietary planning.